Industrial plants include many different types of equipment assets for industrial and/or process automation and systems that require setup, monitoring, control, and/or maintenance. For example, equipment assets in a typical process plant may include field devices, rotating equipment, stationary equipment, and/or electrical power distribution equipment. Field devices may include equipment such as process pressure, temperature, level, and/or analytical measurement devices, flow meters, valve positioners, and/or switches. Rotating equipment may include equipment such as such as motors, pumps, compressors, and/or drives. Stationary equipment may include equipment such as mechanical vessels tanks, pipes, and so on. Electrical power distribution equipment may include equipment such as such as switch gear and/or motor control centers. Other assets may also be used.
Process control systems in an industrial plant, like those used in chemical and petroleum processes, typically include one or more process controllers communicatively coupled to at least one host or operator workstation and to one or more field devices via analog, digital, or combined analog/digital buses. The field devices, which may be, for example, valves, valve positioners, switches, and transmitters (e.g., temperature, pressure, and flow rate sensors), perform functions within the process plant, such as opening or closing valves and measuring process parameters. The process controllers receive signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices, use this information to implement control routines, and subsequently generate control signals that are sent over the buses or other communication lines to control the operation of the field devices. With the information collected from the field devices and process controllers, an operator or a technician can execute one or more applications at an operator workstation that perform any desired function with respect to the process, such as, for example, configuring the process, viewing the current state of the process, and/or modifying the operation of the process.
In many cases, field devices and other industrial and/or process automation equipment assets may require on-site setup, configuration, testing, and maintenance. For example, before a field device can be installed at a particular location at a process control plant, the field device may need to be programmed and may then need to be tested before and after the field device is installed. Field devices that are already installed may also need to be regularly checked for maintenance reasons or, for example, when a fault is detected and the field device needs to be diagnosed for service or repair. Generally speaking, configuration and testing of field devices are performed on location using a handheld, portable maintenance tool. Because many field devices are installed in remote, hard-to-reach locations, it is more convenient for a user to test the installed devices in such remote locations using a handheld, portable tool rather than using a full configuration and testing device, which can be heavy, bulky, and non-portable, generally requiring the installed field device to be transported to the site of the diagnostic device.
In the case in which a field device or other equipment asset is at least partially operational and supplied with power via a local bus, a handheld maintenance tool or portable testing device (“PTD”) can connect to a communication terminal of the field device to run a diagnostic routine. Generally, the field device and the PTD communicate over a two-wire or a four-wire communication connection or line, typically referred to as a bus. For example, FOUNDATION® Fieldbus devices and HART® devices are typically connected to a two-wire (or in some cases a four-wire) connection line or bus when installed in a plant environment. It is known to use a handheld device to connect to, for example, a Foundation Fieldbus or a HART communication line or other communication bus to communicate with devices connected to that communication line or bus.
In some cases, testing a field device or other equipment asset on location may not be possible unless power is supplied to the field device. This may occur, for example, when there is a power outage, when there is a power issue localized to the field device itself, or when one or more field devices are offline, i.e., in fault situations. Generally, power may be provided to the field device by connecting the field device to a power source via a two-wire power line. For example, FOUNDATION® Fieldbus devices are powered via the same terminals used for communicating with the fieldbus device. However, portable power considerations and Intrinsic Safety (“IS”) standards restrict the manner in which power can be provided to a field device, especially when the field device is installed in a critical or dangerous process control system in the field.
In some cases, Intrinsic Safety (“IS”) standards restrict the manner in which power and other communication signals can be provided to a field device or other equipment asset, especially when the equipment asset is installed in a critical or dangerous process control system in the field. Generally, IS considerations and design is focused on limiting the amount of energy available that could cause a spark sufficient to cause an ignition in a hazardous area with an atmosphere with an elevated chance of being highly flammable or explosive. For example, higher voltages are used for providing power to the field devices than the voltages that are used for communicating with the field devices. Additionally, certain safety measures must be implemented before powering a field device in the field. In particular, according to IS guidelines, a technician cannot switch on the power of a field device within the field device itself and cannot use devices that generate voltages over certain predetermined levels. The IS guidelines prohibit internal power switching and generation of larger voltages because field devices are often installed in proximity to volatile substances or volatile processes, and thus there is higher possibility of causing an explosion by arcing or generating sparks when a high voltage or a power connection is applied to the field device. For reference, an internal switch may be considered any switch that is integrally connected within or physically housed within a field device and/or that is fixed to the field device. Accordingly, the technician servicing the field device cannot use or install a switch within the field device to switch on the power to the device from a provisioned or redundant power line. In addition, IS considerations typically consider not only voltage, but also current, power, capacitance, inductance, and temperature/heat production.
Related IS guidelines also advise against switching on power within a PTD that is connected to a field device or other equipment asset and that is located within a vicinity of the field device. IS standards generally require manual intervention when applying power to a non-operating or a non-powered field device installed in the field. Although it may be desirable to configure existing PTDs with automatic power functions for powering a field device, this configuration is generally prohibited under the IS standards, especially when providing higher power signals to the field devices for powering the field devices or for testing purposes.
To comply with IS standards, some existing PTDs include an interface with four connection ports for coupling four lines or wires between the PTD and a field device or other equipment asset undergoing testing. Generally, a first pair of lines is used for transmitting communication signals at a first voltage range and a second pair of lines is used for powering the field device at a second and higher voltage or voltage range. The first pair of lines is primarily used whenever the field device is undergoing testing, and the second pair of lines/wires is used only when power is needed to be provided to the field device to enable the field device to execute a function (e.g., a test function or a configuration function). In this manner, additional power to the field device undergoing testing always requires manual intervention that includes connecting additional wires between the field device and the PTD. In short, IS standards have generally limited the development of portable field device testing equipment to require two separate sets of lines or lead sets and three or four ports for connecting a field device to the portable testing equipment.
Maintenance technicians in the process industries perform a wide variety of different tasks in a process plant, such as installation of instruments and other equipment assets, configuration and set-up, calibration, data collection, and troubleshooting of instruments and measurement loops. Performance of these different tasks typically requires a myriad of ever-changing portable tools, including, communicators, calibrators, power supplies, data collectors, analyzers and digital multimeters (DVM's), each with its own unique user interface, menus, and displays.
Installing and maintaining instruments and other equipment assets in a typical process plant requires multiple portable tools, such as a communicator for initial set-up and configuration, a calibrator for verification and adjustment of instrument output, and a digital multimeter for troubleshooting of loop wiring, connections, power supply, and the instrument itself. For example, maintaining rotating equipment (e.g. motors, pumps, and generators) may require additional tools for collecting and analyzing vibration data used to detect impending failure.
The potential presence of explosive gasses or dusts often pose additional requirements that these portable tools be tested and certified by agencies such as Factory Mutual or Canadian Standards Association, in order to be certified as intrinsically safe for use in hazardous areas, such as the IS standards discussed above. As a result, technicians often need to acquire and/or carry multiple specialized portable tools into the plant in order to perform the required work.
In view of these current conditions, it would be advantageous to reduce the number of tools that the maintenance technician needs to carry and work with in the process plant while installing and/or otherwise working on field devices in the process system.